Objective: The objective of the study was to determine whether periodontal disease is associated with delivery of a small-for-gestational-age infant. Study design: In a prospective study of oral health, periodontal disease was categorized as health, mild, or moderate/severe on the basis of clinical criteria.Small for gestational age was defined as birth weight less than the 10th percentile for gestational age. A risk ratio(95th percentile confidence interval) for a small-for-gestational-age-infant among women with moderate or severe periodontal disease was calculated. Results: Sixty-seven of 1017 women (6.6% ) delivered a small-for-gestational-age infant, and 143 (14.3% ) had moderate or severe periodontal disease. The small-for-gesta-tional-age rate was higher among women with moderate or severe periodontal disease, compared with those with health or mild disease (13.8% versus 3.2% versus 6.5% ,P < .001). Moderate or severe periodontal disease was associated with a small-for-gestational-age infant, a risk ratio of 2.3 (1.1 to 4.7), adjusted for age, smoking, drugs, marital and insurance status, and preeclampsia. Conclusion: Moderate or severe periodontal disease early in pregnancy is associated with delivery of a small-for-gestational-age infant. Understanding the mechanism of periodontal disease-associated adverse pregnancy out comes could lead to interventions to improve fetal growth. Objective: The objective of the study was to determine whether periodontal disease is associated with delivery of a small-for-gestational-age infant. Study design: In a prospective study of oral health, periodontal disease was categorized as health, mild, or moderate / severe on the basis of clinical criteria. Small for gestational age was defined as birth weight less than the 10th percentile for gestational age. A risk ratio (95th percentile confidence interval) for a small-for-gestational-age-infant among women with Results: Sixty-seven of 1017 women (6.6%) delivered a small-for-gestational-age infant, and 143 (14.3%) had moderate or severe periodontal disease. The small-for-gesta -tional-age rate was higher among women with moderate or severe periodontal disease, compared with those with health or mild disease (13.8% versus 3.2% versus 6.5%, P <.001). Moderate or severe periodontal disease was associated with a small -for-gestation al-age infant, a risk ratio of 2.3 (1.1 to 4.7), adjusted for age, smoking, drugs, marital and insurance status, and preeclampsia. Conclusion: Moderate or severe periodontal disease early in pregnancy is associated with delivery of a small- for-gestatio nal-age infant. Understanding the mechanism of periodontal disease-associated adverse pregnancy out since could lead to interventions to improve fetal growth.